U.S. Pat. No. 5,883,303 discloses and describes an apparatus and method for pigging, flooding and pressure testing pipelines.
The above patent is directed to the testing required when a new pipeline is placed in operation. However, when commissioning a subsea pipeline, or adding a new segment to an existing offshore pipeline, it is often desired to follow the hydrostatic pressure testing with an inert gas or specified medium to purge/dewater from the subsea pipeline, and/or inject specified chemicals, to dry the inside of the line before flow of the oil/gas in the pipeline.
The dewatering of a subsea pipeline by the prior art has been at surface level, usually on a surface vessel, boat, structure or platform. This requires that long lines of coiled tubing, hose, or pipe, be used if at least one end of the pipeline is not at the surface. The prior art method for dewatering uses large distances of coiled tubing, hose, or pipe, to connect the pipeline to a high volume, high pressure compressor mobilized on the deck of a platform or support vessel to remove the water and dry the line before product is allowed to pass through the line. Also required by the prior art method are large compressors, compressor boosters and surface support vessel and/or vessels, to support the large volume of compressed gases needed to fill the new portion of the pipeline with the gas to purge the water from the pipeline.
The method of the present invention eliminates the larger volume of compressed gas, the higher pressure of the compressed gas, the large pumps/compressors, compressor boosters, long distances of coiled tubing/hose/pipe, and substantial surface support vessel/vessels, all required by the prior art methods.
The following United States Patents were cited in the parent application:
U.S. Pat. No. 3,640,299 discloses a fluid energized control system for controlling the valves of subsea wellheads.
U.S. Pat. No. 3,777,499 discloses a method for recovering the end of a damaged line from the bottom of a body of water by introducing gas into one end of the line and pumping liquids from the other end until a section of the line at least sufficiently long to reach the surface is made light enough to lift without breaking under its own weight.
U.S. Pat. No. 3,961,493 discloses a typical method for removing water from a subsea pipeline by compressed gas. Compressed gas is introduced into a pipeline behind a pig forcing the water out the other end. There is no pump disclosed.
U.S. Pat. No. 4,234,268 discloses apparatus for recovering by means of a pipeline craft, pipes laid on deep sea beds.
U.S. Pat. No. 4,906,136 discloses a method for connecting a conduit to a subsea structure and a device for use in connecting a conduit end to a subsea structure.
U.S. Pat. No. 5,044,827 discloses a method for severing and recovering a submerged pipeline.
U.S. Pat. No. 5,273,376 discloses an emergency release tool for operation by a remotely operated vehicle (ROV) for forcefully releasing a riser from a subsea well assembly.
U.S. Pat. No. 5,927,901 discloses an underwater pipeline apparatus for the free flooding, using the head of water above the subsea pipeline, to force a pig through the pipeline and flood (fill with water) a pipeline that is filled with a gas. In the event that the head of water is insufficient to force the pig completely to the end, the apparatus has a pump that may be operated from the surface or from a remotely operated vehicle to complete the flooding.
U.S. Pat. No. 6,022,421 discloses a method for sensing and launching pipeline pigs into a pipeline.
U.S. Pat. No. 6,145,223 discloses a dredging apparatus fpr the removal of cuttings gathered around a bore hole mouth on the seabed including an ejector coupled to a suction hose and a conveyor pipe.
U.S. Pat. No. 6,454,492 discloses a pig launching system and a pig receiving system for use in cleaning a subsea flowline.
US 2003/0170077 A1 discloses riser systems and methods for raising production fluid within the riser system downstream of a subsea source or plurality of sources.